Pathogenic mechanisms of diarrhoea

Question 1

What are the pathogenic mechanisms leading to diarrhoea?

Answer 1

Hypersecretion
Villous atrophy
Infiltrative and proliferative distortion of mucosa
Mucosal necrosis

Question 2

Describe hypersecretion caused by pathogens

Answer 2

Enterotoxins can trigger crypt cells to pump Cl- into crypt space => attracts Na+ => increased local osmotic pressure => water pulled into intestines
e.g., enterotoxigenic E.coli (ETEC)

Question 3

Describe infiltrative and proliferative distortion of mucosa leading to diarrhoea

Answer 3

Recruitment of large numbers of macrophages and T cells in lamina propria and sub-mucosa => crypt compression and villous distortion => reduces absorptive capacity
e.g., Paratuberculosis (Johne’s disease)

Question 4

Describe mucosal necrosis leading to diarrhoea

Answer 4

Pathogen infection leads to cell death => reduced absorption
e.g., brachyspira